1. Field of the Invention
The present invention relates to a manufacturing method of semiconductor devices.
2. Related Background Art
Recently, a sidewall transfer process has been proposed and used to realize finer patterning. According to the sidewall transfer process, patterns of a photo-resist are formed whose pitch is twice a target line width, the photo-resist is slimmed, an under-layer film is processed to form a core material pattern, a sidewall is deposited, the core material is removed, and the under-layer film is further processed to form a pattern having a line width smaller than a lithographic limit (see Japanese Patent Laid Open Pub. No. 2006-303022).
However, in a trial for further finer patterning, the top of a component of the sidewall, for example, an amorphous silicon film had once warped inward, that is, toward a side where the core material pattern existed when the under-layer film was being processed, thus resulting in a problem that the under-layer film could not be processed so as to have a predetermined design value. Such a problem was not observed with a pattern size of about 32 nm and may pose an obstacle to forming an interconnection line or shallow trench isolation (STI) pattern in a future, attempt to realize a pattern size of 30 nm or less.